Page views: we count a page view every time a page is loaded on your website.
Popup displays: we count a display every time a popup is displayed. When the tab is activated before the popup, we count a display when the tab is clicked.
Clicks: we count a click every time one of your visitors click on a call to action (sign up, image, etc.). This excludes clicks to close the pop-up or untracked clicks.
Emails: we count an email each time you collect a new email.
CTR is the click-trough-rate, i.e. Clicks/Displays.